Nonvolatile memories are used to store important information, such as the code that runs the machines in which these memories are used. Consequently, most non-volatile memory devices do not allow a simple write command to change the data in the memory device. As a safety precaution, to insure code and data integrity, a sequence of write operations with specific data and addresses are required to initiate the programming or erasing of data in a location of the memory device.
With today's devices becoming faster, using wider data widths (data words having an increased number of bits per word), and requiring the use of lower power devices, circuit design and system design are becoming a more complex task. Adding to the design complexity for a non-volatile memory, such as a synchronous Flash memory, is the need to satisfy the speed, density, and power requirements along with the requirement of completing a sequence of write operations prior to the actual programming or erasing of a non-volatile memory.
For example, a synchronous Flash memory operates at speeds exceeding 100 MHz. Operating at such speeds requires a read or write cycle timing of less than 10 ns. Additionally, the design criteria for this high speed device requires that the Flash memory must accommodate a 32 bit wide data bus. Further, with some forms of Flash memory also required to operate at 1.8 V, associated specifications lead to aggressive current consumption.
With the synchronous Flash memory operating at a high speed, where it may receive a command at any moment, all address and data buffers of the Flash memory are in a powered up state. Additionally, detection circuitry used to receive signals for command execution are also in an on state. Consequently, a significant portion of the circuits within the synchronous Flash memory are continually configured in an on state. As long as the system using the Flash memory is providing power, the Flash memory will be creating a current consumption issue.
For these and other reasons there is a need for the present invention.